JPH02234340A - Ion current measurement system for ion implantation equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ion current measurement system for an ion implantation device, and is particularly suitable for integrating with an electron shirt and suppressing charging of a wafer that is an implanted object. The present invention relates to an ion current measurement system.

[Conventional technology]

The ion current measurement system of conventional ion implantation equipment is, for example,
Special Publication No. Sho 58-42939 and Special Publication No. Sho 58-4
As shown in Japanese Patent No. 3861, a portion of the Faraday cup is negatively biased. Also,
As shown in Japanese Patent Laid-Open No. 62-103951, the Faraday and the disk are almost at ground potential, or as shown in Japanese Patent Laid-Open No. 62-10395, only the disk is at ground potential. Some were positively or negatively biased.

[Problem to be solved by the invention]

The above conventional technology has no problems as a basic configuration, but
If a gap occurs between the Faraday and the disk in a high-current ion implantation device, there is a concern that charge may leak from this gap. In this case, it is mainly electrons that leak. It is thought that most of the positive ions including secondary ions are implanted or attached when they collide with the disk or Faraday wall surface. In particular, when a large amount of electrons are emitted from an electron source or the like for the purpose of preventing static electricity, the phenomenon of leakage may appear most conspicuously.

When a faraday and an electron source are combined as in the prior art described above, when electrons leak, the potential of the entire current measurement system including the faraday increases.

Therefore, current flows through the ion ammeter. That is, the leakage of electrons is directly measured by the ion ammeter. When electron leakage occurs during implantation, the ion ammeter indicates the sum of the net ion current and the electron leakage current. In other words, it shows a value greater than the net ion current. Therefore, a phenomenon occurs in which the total ion implantation amount is lower than the desired ion implantation amount.

In order to suppress electron leakage, some devices are equipped with an electron suppressor using a magnetic field or an electric field near the Faraday exit, but when using an electric field suppressor, it is difficult to apply high voltage if the implanted object is particularly susceptible to charging, such as a semiconductor wafer. There is a concern that if the applied sub-pressure sensor is located near the semiconductor wafer 81, charges will be induced in the elements on the wafer, causing destruction of the elements. In addition, in the case of suppressors using magnetic fields, if the wafer is placed on a disk that is rotating at high speed, there is a concern that depending on the direction of the magnetic field, a voltage may be generated within the element, leading to destruction. An object of the present invention is to provide an ion current measurement system for an ion implantation device that can suppress electron leakage and accurately measure ion current.Another object of the present invention is to easily suppress electron leakage. The objective is to provide an ion current measurement system for an ion implantation device that can perform Still another object of the present invention is to provide an ion current measurement system for an ion implantation apparatus that can suppress leakage of electrons without adversely affecting the target semiconductor device. Still another object of the present invention is to provide an ion current measurement system for an ion implantation device that does not cause the ion current measurement system to malfunction even if electrons are emitted within the Faraday. (Means for Solving the Problems) The above purpose is to apply a positive voltage to the ion current measurement system in the ion implantation device, that is, to all parts such as the Faraday glass and the disk that make up the Faraday cup, and to This is achieved by configuring the chamber to have a positive potential.The energy of the secondary electrons generated when ions are irradiated onto the target is several tens of eV at most.Therefore, it is necessary to prevent these electrons from leaking. To suppress this energy, apply a potential to the target and other objects corresponding to a potential exceeding this energy.For example, if the energy of secondary electrons is 10 eV, applying a voltage of 15 to 20 V to the Faraday and the disk will suppress these two. Leakage of secondary electrons can be prevented.

Furthermore, in order to suppress leakage of electrons emitted from the electron source within the Faraday, a voltage higher than the electron extraction voltage of the electron source may be applied. At this time, the potential of the electron source becomes slightly positive with respect to the grounded vacuum chamber. The electron extraction voltage of an electron source is generally 100V to IKV or more. However, the voltage applied to the current measurement system does not actually need to be so large, and electron leakage can be almost suppressed at a voltage of 10 ov or less. The power supply for voltage application may be inserted between the ion ammeter and the ground, but it is better to insert it between the electrode such as a Faraday cup in the vacuum chamber and the ion ammeter, which will improve the ammeter and ion current measurement. It is easy to handle the electronic circuits related to the system at ground potential.

[Effect]

A positive voltage is applied to the disk, Faraday cylinder, etc. that constitute the Faraday cup with respect to the vacuum chamber. If this voltage is sufficiently larger than the energy of the electrons attempting to leak, there is no risk of electrons leaking from the Faraday measurement system into the chamber. From the perspective of Faraday and the disk, the chamber is at a negative potential. Therefore, it can be said that the electrons leaking from Faraday do not reach the chamber due to the force of the negative potential. Since the ion current measurement system is at the highest potential within the vacuum chamber, even if one carrier electron leaks out of the ion current measurement system, it will be attracted back to the ion current measurement system and returned.

Therefore, malfunction of the ion ammeter due to electron leakage can be suppressed.

It is desirable to keep the Faraday tube and the gap between the tube and the disk sufficiently small to prevent secondary ions from leaking. Also, install Farade's negative voltage suppressor as usual.

When applying a potential difference between the disk and the Faraday cylinder, it is desirable to apply a voltage superimposed on the voltage applied to the entire ion current measurement system. That is,
When there are multiple potentials, it is desirable to configure the structure so that the lowest potential among them is sufficient to suppress leakage of electrons.

When a voltage is applied to a water-cooled component such as a disk, if the cooling water is conductive, the cooling water piping becomes a path for leakage current. To do this, a metal part such as a union that can be used as an electrode is inserted in the middle of the pipe. Then, this electrode portion is connected to the negative output of the voltage power source.

This makes it possible to cut the voltage so that the voltage is not applied over the entire length of the water pipe between the disk and other parts at ground potential. It goes without saying that the piping must be non-conductive.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to FIG.

FIG. 1 is a configuration diagram showing an embodiment of the ion current measurement system of the ion implantation apparatus of the present invention, and FIGS. 2 to 4 each show an embodiment of the bias voltage source of FIG. 1. be.

In FIG. 1, when an ion beam 1 is guided into an implantation chamber vacuum chamber 2 of an ion implantation apparatus, it passes through a Faraday cylinder 3 and is implanted into a wafer 5, which is an object to be implanted, on a disk 4. The current of ions implanted into the wafer 5 and disk 4 is measured by an ion ammeter 6 via wiring. Secondary ions and secondary electrons generated when the ion beam 1 is implanted into the wafer 5 are captured by the Faraday cylinder 3. Further, the Faraday tube 3 is provided with an electron source 7 for charge neutralization, and electrons 9- are extracted by an electron extraction voltage g8. A positive potential is applied to all components within the vacuum chamber 2 by a bias voltage source 10. This allows Faraday tube 3 and disk 4 to
The electrons 11 leaking through the gap are drawn back to the disk 4 and the like. Therefore, the ammeter 6 is prevented from malfunctioning due to electron leakage.

In order to suppress the leakage of electrons from the cooling water piping 12 of the disk 4, etc., a metal joint 13 such as a union is inserted into the piping. At this time, the metal joint 13 and the joint of the disk 4 are preferably made of stainless steel. Then, the wiring between the bias voltage source 10 and the ammeter 6 and the metal joint 13 are connected. Thereby, voltage is applied only between the disk 4 and the metal joint 13. Since no voltage is applied between the metal joint 13 and the component 14 at ground potential, no current flows and no electron leakage occurs.

The bias voltage source 10 is required to be a voltage source in which current can flow in the opposite direction to the polarity of the output, that is, to be able to normally output an output even if current flows in from the positive side and current flows from the negative side.

A normal voltage power supply does not allow current in two opposite directions, but if you configure it so that a voltage is generated by passing current through the resistor R, as shown in Figure 2, you can use a normal power supply. It is also effective to use a Zener diode DI as shown in FIG. Furthermore, in place of the resistor R in FIG.
It is also effective to use a Zener diode D2 as shown in the figure.

In FIG. 1, the electronic suppressor at the entrance of the Faraday cylinder 3 and the scanning mechanism for the disk 4 or the ion beam 1 are not shown. In practice, these are constructed using conventional techniques.

The voltage application method shown in FIGS. 2 to 4 can also be used when voltage is applied individually to the Faraday tube 3, the disk 4, and other individual components.

Although this embodiment has been described with respect to a large current type ion implantation device, it is also applicable to a medium current type or other ion implantation device.

〔Effect of the invention〕

According to the present invention described above, it is possible to easily prevent leakage of electrons from the ion current measurement system during implantation without changing the configuration of the implantation chamber of a conventional ion implantation device, and to improve accuracy. The ion current is measured, making it possible to obtain accurate implantation amount and good implantation uniformity. Especially, even if a large amount of electrons are emitted in the implantation chamber for the purpose of suppressing static electricity during implantation, This has the effect of allowing implantation to be performed without adversely affecting the amount or the like.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the ion current measurement system of the ion implantation apparatus of the present invention, and FIGS.
FIG. 2 is a diagram illustrating an example of the bias voltage source shown in FIG. 1... Ion beam, 2... Implanting chamber vacuum chamber,
3... Faraday tube, 4... disk, 5... wafer 6... ion ammeter, 7... electron source, 8...
-Electron extraction voltage power supply, 9...electron, 10...bias voltage source, l1...leakage electron, 12...cooling water piping, 13...metal joint.

Claims (1)

[Claims] 1. All the components related to the ion current measurement system in the vacuum chamber of the implantation chamber of the ion implantation device are configured to have a positive potential with respect to the chamber. Ion current measurement system for ion implantation equipment. 2. An ion current measurement system for an ion implantation apparatus according to claim 1, wherein the electron source and the ion current measurement system are electrically connected. 3. Among the secondary electrons generated during ion implantation, the component parts are brought to a potential higher than the potential corresponding to the energy of the electrons leaked out of the Faraday cup formed by the component parts related to the ion current measurement system. An ion current measurement system for an ion implantation apparatus according to claim 1, which is configured to: 4. The components of the ion current measurement system are heated to a potential higher than the energy of secondary electrons generated during ion implantation or electrons generated from the electron source that can leak out of the Faraday cup. An ion current measurement system for an ion implantation apparatus according to claims 1, 2, and 3, which is configured to have the following characteristics. 5. Insert a bias voltage source so that all or individual components related to the ion current measurement system in the vacuum chamber of the implantation chamber of the ion implantation device have a positive potential, and the bias voltage source An ion current measurement system for an ion implantation device that allows a current of opposite polarity to the output to flow through the voltage source. 6. The ion current measurement system for an ion implantation apparatus according to claim 5, wherein a constant voltage power supply is used as the bias voltage source, and resistors are inserted between the positive and negative outputs of the constant voltage power supply. 7. An ion current measurement system for an ion implantation apparatus according to claim 5, which uses a Zener diode as the bias voltage source. 8. Claim 5, wherein the bias voltage source is inserted between an ion ammeter or an electronic circuit for measuring ion current and a component for measuring ion current in the vacuum chamber of the implantation chamber. Ion current measurement system for ion implantation equipment. 9. The cooling water wiring for cooling the component to which a voltage is applied is composed of a non-conductive tube, and the component is connected between the component and a component for supplying and discharging the cooling water that is at ground potential. 9. The ion current measurement system for an ion implantation apparatus according to claim 8, wherein an electrode is inserted into a wiring joint, and the electrode is wire-connected between the voltage source and the ion ammeter. 10. The ion current measurement system of the ion implantation apparatus according to claim 9, wherein the pipe joint to which the component to which voltage is applied is connected and the electrode inserted into the pipe joint are made of stainless steel. .